The present invention relates to a coil unit of an operating electromagnet mounted on an electromagnetic contactor, and in detail, to a terminal structure of a coil with a coil strand wound on a bobbin, and to an assembling method of a coil unit to which the terminal structure is adopted.
For a coil unit of an operating electromagnet opening and closing main circuit contacts of an electromagnetic contactor, a single coil unit is generally known in which an assembly having a coil with a coil strand wound on a bobbin is mounted on a central leg of an E-shaped stationary core. In addition, a double coil unit (DC excitation system) is known in which the coil unit is divided into two sets of single coil units to be respectively mounted on right and left legs of a U-shaped stationary core with coils of the respective coil units made coupled in series for being connected to an operating circuit (See, for example, “A structure of an electromagnetic contactor and designations of parts thereof, SC-N6”, (online) Fuji Electric Technica Co., Ltd., [Retrieved on Aug. 30, 2008], Internet URL:http://www.fe-technica,co.jp/html/shohin/41/pdf/AH294_P1—10-17.pdf>).
The structure of an electromagnetic contactor mounting the related double coil unit, described in the foregoing non-patent document, for an operating electromagnet and the structure of the related double coil unit are shown in FIG. 8A to FIG. 10D. First, in FIGS. 8A to 8C, the electromagnetic contactor is formed of a main body case 1, a power supply side main circuit terminal 2, a load side main circuit side terminal 3, stationary contactors 4 and 5, a bridging movable contactor 6, a movable contactor holder 7, a movable core 8 of an operating electromagnet, a two-leg stationary core 9 of soft-iron, a back spring 10, a double coil unit 11, a pair of extension leads (insulated covered wires) 12, a printed-circuit board 13 of an operating circuit and external terminals 14 of the operating circuit. In the foregoing, the main body case 1 is formed with a structure dividable into three of a lower case 1a, an upper case 1b and an arc-extinguishing chamber cover 1c. The two-leg stationary core 9 is formed of a yoke 9a, a left leg 9b and a right leg 9c. The back spring 10 energizes the movable core 8 toward the release side. The double coil unit 11 has equally specified two sets of single coil units 11A and 11B, each having a coil 16 with a coil strand wound around a bobbin 15 of molded resin, combined to be mounted on the left leg 9b and the right leg 9c, respectively, of the stationary core 9. A pair of the extension leads 12 are connected to their respective single coil units 11A and 11B to be taken out therefrom. Moreover, reference numerals 9b-1 and 9c-1 denote magnetic pole plates of the left leg 9b and the right legs 9c, respectively, of the stationary core 9 and reference numeral 12a denotes a connector for making each of the extension leads 12 have a plug-in connection to the printed-circuit board 13.
Next, the assembled structure of each of the aforementioned single coil units 11A and 11B is shown in FIGS. 9A to 9E. Each of the single coil units 11A and 11B has a structure having a coil 16 with a coil strand wound around the bobbin 15 of molded resin. The bobbin 15 has flanges 15b and 15c at the upper and lower ends, respectively, of a barrel 15a. On the rim of each of the flanges 15b and 15c, a coupling tab 15d and an engaging projection 15e are formed which are used when coupling the single coil units 11A and 11B as will be described later. Moreover, the coil 16 is formed by winding a coil strand (an enameled wire, for example) around the barrel 15a of the bobbin 15 and wrapping the outer surface of the wound coil strand with insulating tape 17 with the initial side lead wire 16a and the final side lead wire 16b, each being a part of the coil strand, being taken out from the bobbin 15.
In each of the single coil units 11A and 11B, for forming the coil 16 with the coil strand wound around the bobbin 15, the initial side lead wire 16a is first temporarily fastened on the surface of the barrel 15a of the bobbin 15 with a piece of adhesive tape 18 before the coil strand is wound around the barrel 15a by an automatic coil winding machine. The final side lead wire 16b is also temporarily fastened on the coil 16 with a piece of adhesive tape 18 in the same way as above. Finally, by wrapping the outer surface of the coil 16 with a strip of insulating tape 17, each of the single coil units 11A and 11b is completed.
Next, the assembled structure of the double coil unit 11 with aforementioned two sets single coil units 11A and 11B arranged side by side to be combined are shown in FIGS. 10A to 10D. Namely, the single coil units 11A and 11B are combined by coupling their respective bobbins 15 with the flanges 15b at the upper ends made butted against each other and the flanges 15c at the lower ends made butted against each other, in which the coupling tabs 15d are made engaged with the engaging projections 15e mated thereto. Then, as shown in a connection diagram given as FIG. 10D, the final side lead wires 16b of the single coil units 11A and 11B are twisted together to be joined and soldered (W: solder). Moreover, the initial side lead wire 16a of each of the single coil units 11A and 11B and the strand of the extension lead 12 for external connection are twisted together to be joined and soldered. Furthermore, a strip of the insulating tape 17 is wound around the outer surfaces of the coils 16 of the single coil units 11A and 11B so as to wrap the coils 16 together and cover the soldered junction of the final side lead wires 16b and each soldered junction of the initial side lead wire 16a and the strand of the extension lead 12 for external connection. Thus, the coils 16 are coated for insulation for being provided as the assembly of the double coil unit 11.
Thereafter, the assembly of the aforementioned double coil unit 11 is, as was explained with reference to FIGS. 8A to 8C, made fitted to the left leg 9b and the right leg 9c of the stationary core 9 to be mounted on the lower case 1a of the electromagnetic contactor. Then, the connectors 12a of each of the extension leads 12 is made to have a plug-in connection to the circuit on the printed circuit board 13.
Incidentally, the aforementioned coil unit with the related structure has the following problems in ease of assembling. First, in assembling each of the single coil units 11A and 11B, in the step of forming the coil 16 with a coil strand wound around the bobbin 15, troublesome manual work is required in which each of the initial side lead wire 16a and the final side lead wire 16b of the coil 16 is temporarily fastened with a piece of the adhesive tape 18. Second, in the step of forming the double coil unit 11 by combining two sets of the single coil units 11A and 11B, time consuming work process is required in which the final side lead wires 16b of the single coil units 11A and 11B are twisted together to be soldered by manual work, and the initial side lead wire 16a and the extension lead 12 for external connection of each of the single coil units 11A and 11B are also twisted together to be soldered by manual work. Therefore, in an assembling process of the coil unit, there are many working processes carried out by manual work to cause the products to be high in cost.
The invention was made in view of the foregoing with an object of providing a coil unit of an electromagnetic contactor in which unit a coil strand can be wound with reduced working man-hours of manual work and, together with this, the terminal structure of the coil is improved so that the connection of the lead wires of the coil and the connection of the lead wire of the coil and an extension lead can be carried out with a simple single plug-in operation without requiring soldering, and providing an assembling method of the coil unit.